Solid particle transfer process and apparatus



May 20, 1958 2,835,537

soLin PARTICLE TRANSFER PROCESS AND APPARATUS Filed Nov. s, 1955 D. A. DAVIS, JR

2 sheets-sh eet l INVEN TOR.

DAMON DAV/5,.J'R. BY

HAS .4 TTORNQ Y SOLID PARTICLE TRANSFER PROCESS AN APPARATUS 6 Claims.

This invention relates to improved process and apparatus for conveying solid particles from a low pressure zone to a high pressure zone.

In my copending applications Serial Numbers 236,5 37-9 filed July 13, 1951, (now Patents 2,726,135-7 dated December 6, 1955), l have described process and apparatus for introducingsolid particles into a high pressure zone from a low pressure zone. The basic principle for accomplishing this involved forming the solid particles into a compact column, positioning a vent between the ends of the compact column and providing the ventwith means which would permit flow of gas through the vent but prevent flow of solid particles through the vent. One end of the column was exposed to the high pressure zone while the opposite end of the column was exposed to the low pressure zone. a relatively small how of gas through the column of solid particles from the high pressure zone out through the vent. At the same time the compact column prevented a major flow of gas and, due to pressure drop caused by this flow through the compact column, the flow of gas was reduced to a small amount. The compact column was in this manner stabilized so that the pressure was dispersed through the walls of the apparatus holding the compact column. In order to introduce solid particles into the high pressure zone, the solid particles were introduced into the low pressure end of the compact column which was then subjected to elevated pressure and the vent for gases was closed. Introduction of high pressure gas into the low pressure end of the column then raised it to elevated pressure slightly above that existing in the high pressure zone. This caused the column to become unstable and resulted in flow of solid particles into the high pressure zone.

This invention has for its object to provide improved procedure for continuously or intermittently introducing solid particles from a low pressure zone into a high pressure Zone. Another object is to provide improved procedure and apparatus for introducing particles into a high pressure zone utilizing the principle of a compact column with an intermediate vent wherein centrifugal force is utilized to cause the flow of the solid particles as a compact column into the high pressure zone. Other objects will appear hereinafter.

These and other objects are accomplished by my invention which includes forming the solid particles which are to be introduced into the high pressure zone into a compact column by centrifugal force, exposing the end of the compact column which is subjected to the highest centrifugal force to the high pressure zone into which the solid particles are to be introduced, adding solid particles to that end of the compact column which is subjected to the lowest centtrifugal force, venting gas which leaks through the compact column from the high pressure zone at a vent positioned intermediate the ends of the compact column, preventing flow of solid particles through the vent, removing solid particles from the end of the compact column which is subjected to the highest The vent for the gas permitted United States Patent 2,335,537. Patented May 20, 1958 centrifugal force, and conveying the removed solid particles into the high pressure system. My invention also includes means for conveying solid particles from a low pressure to a high pressure zone comprising an axially mounted rotatable chamber adapted to hold a compact column of solid particles, means for removing solid particles from a point in the rotatable chamber removed from the axis, means for introducing solid particles into the rotating chamber at a point near its axis and a vent positioned intermediate the ends of the rotatable chamber which vent is adapted to allow passage of gas but prevent passage of solid particles therethrough.

in the following description I have set forth several of the preferred embodiments ofrny invention, but it is to be understood that they are given by way of illustration and not in limitation thereof.

in the accompanying drawings wherein like numbers refer to like parts:

Figure l is an elevation partially in section of my improved apparatus for introducing solid particles into a high pressure system;

Figure 2 is a view partly in section of the apparatus illustrated in Figure 1 taken on line 22 of Figure 1;

Figure 3 is a view partly in section taken on line 3-3 of Figure l; I

Figure 4 is a diagrammatic elevation showing a high pressure reaction system which utilizes the apparatus of my invention for introducing solid particles into a high pressure reactor;

Figure 5 is a fragmentary drawing of a modification of the apparatus illustrated in Figure 4; and

Figure 6 illustrates the manner in which the difierential centrifugal force .varies with radius.

Referring to Figures 1, 2 and 3, numeral 6 designates a rotatable casing having the form of an elongated cylinder which tapers at the ends and is closed at the ends by plates 8. Casing 6 is provided with an integral hollow axis it) which is rotatably mounted in packed hearing 12, the lower portion of which is adapted to be connected to a high pressure zone or system by means of flange l4. Bearing 12 is provided with a conduit 16 into which a scavenging gas under high pressure is introduced. Shaft 10 is driven by pulley 17.

Hollow shaft lt) connects at its upper end to a conduit 18 which is rigidly mounted axially within casing 6. This conduit 18 is open at the ends thereof. Numeral 20 designates a conduit which is connected at its lower end to a conduit 22 which is centrally mounted within conduit 18 and which is open at each end. Conduit 20 is mounted in packed bearing 2 which is stationary and to which is connected stationary conduit 26. Numeral 28. designates a hopper for solid particles which are to be introduced into the high pressure zone. This hopper is provided with a trough 30 for introducing the solid particles into the central opening 32 in casing 6 at a rate controlled by a gate valve 34. Casing 6 is provided with a plurality of vents 36. These vents include a screen 38 or like means for permitting flow of gas from the vent but for retaining solid particles.

In operating the apparatus illustrated in Figures 1, 2 and 3 it is necessary that a packed column of solid particles be established in the rotating arms 6 before the apparatus is connected to or subjected to the high pressure zone into which the solid particles are to be introduced. This is accomplished by causing rotation of casing 6 by power applied to pulley 17 and by introducing solid particles into the central opening 32 of casing 6. These solid particles are caused to assume the form of a compact column by centrifugal force. Thus during rotation the solid particles fill the rotating casing 6 as illustrated by the dots in the drawing. However, the solid particles do not at this stage flow into concentric conduit 18. When the compact condition of solid particles has thus been established, the high pressure is connected to conduit by means of flange 14. Such connection may be effected with a wide aperture valve 19 (see Figure 4) connected between flange 14 and the high pressure chamber or casing. When connection to the high pressure zone has thus taken place, the gas in the high pressure zone will flow through conduit 10 and radially outward through conduit 18. However, the combination of centrifugal force and the pressure dispersing action of the compact column and vents 36 will prevent substantial flow of gas from the ends of conduit 18 either through vents 3.6 or through the central opening 32 of casing 6. At this point a high pressure ga which is somewhat above the pressure existing in the high pressure zone is passed through conduit 26, conduit 20 and conduit 22. This high pressure gas issues from the ends of conduit 22 and this current of high pressure gas removes solid particles from the extremities 8 of the rotating casing 6. These removed solid particles are suspended in the current of gas and this suspension passes radially inward through conduit 18 into the conduit 10 and thence to the high pressure system to which flange 14 is connected.

While this is taking place, solid particles are continuously introduced into opening 32 of easing 6 from hopper 28. The rate of introduction is adjusted by valve 34 so that it will correspond to the rate of removal of solid particles from the ends 3 of rotating chamber 6. In this way centrifugal force causes the solid particles to flow from opening 32 toward the ends 8 of the rotating arm at a rate which is the same as the rate of removal. Thus a compact column of solid particles is maintained at all times in the rotating chamber 6 but there is a simultaneous passage of solid particles from the low pressure opening 32 to the high pressure exit 14. This passage of solid particles does not upset the compact column. In other words the compact column condition is maintained at all times so that the compact column prevents substantial passage of gas from the high pressure zone through the compact column to the opening 32.

Referring to Fig. 4, I will for the purpose of convenience describe the use of my invention for introducing a finely divided hydrogenation catalyst into a high pressure reactor used for destructive hydrogenation of a hydrocarbon. Numeral 50 in Figure 4 designates a low pressure regenerator in which a hydrogenation catalyst is regenerated in order to burn off carbon deposited thereon during the destructive hydrogenation operation. This combustion is accomplished by suspending the particulate catalyst at elevated temperature in a current of gas which includes oxygen. The regenerated solid particles are removed through conduit 52 at a rate controlled by valve 54 and are introduced into the central opening 32 of centrifugal introducing apparatus 6 similar to that illustrated in Figure 1. This introduced catalyst flows through the rotating apparatus in the manner described above and is introduced at high pressure through valve 19 and thence into conduit 56 in the form of a suspension in a gas (preferably hydrogen). This suspension which may be at a high pressure such as 1000 p. s. i. flows into high pressure reactor 58 wherein destructive hydrogenation of a high boiling hydrocarbon such as a reduced crude petroleum is taking place in known manner in the presence of the fluidized hydrogenation catalyst. The charge stock and hydrogen is introduced into the reactor 58 through conduit 60 and reaction products and hydrogen are removed through conduit 62. Entrained catalyst is removed by cyclone separator 63 and returned to the reactor. The reaction conditions in high pressure reactor 58 are preferably about 1000 p. s. i., a temperature of about 825 F. and the catalyst is preferably about 12 percent nickel tungstate deposited upon alumina stabilized with a small amount, such as 5 percent of silica. During this reaction carbon is deposited upon the catalyst. A small stream of catalyst is therefore removed through i conduit 64 provided with a vent 66 which vent is provided with a screen which permits passage of gas but will not permit passage of solid particles.

The catalyst, introduced into the top of conduit 64, is purged with a small amount of steam or inert gas introduced through conduit 65 and then assumes the form of a compact column, the lower end of which is at a relatively low pressure while the upper end of Which is at the high pressure of about 1000 p. s. i. existing in reactor 58. A small amount of the purging gas flows out through the vent 66. Due to the pressure reducing effect of the compact column, the pressure at the lower end of the conduit 64 is substantially atmospheric and the solid particles can be removed from this lower end by means of low pressure current of transport air or other gas passed through conduit 67. The rate of introduction of this transport gas will control the rate of removal of the solid particles from the lower end of compact conduit 64. This rate of removal should be such as to maintain at all times a compact column in conduit 64. The removed solid particles suspended in the transport gas flow through conduit 70 back into regenerator 50 where the catalyst is regenerated and then recycled as described.

Wide aperture valve 19 shown in Figure 4 is subject to rapid wear or erosion by the solid particles passing therethrough and by the closing of the moving parts of the valves such as the gate upon solid abrasive particles. For this reason it is desirable to avoid the use of such a valve whenever feasible. Figure 5 illustrates a modification of the apparatus illustrated in Figure 4 whereby the use of a valve having moving parts may be avoided.

Referring to Figure 5, numeral designates a vertical conduit adapted to hold a column of packed solid particles which will act as a seal or valve permitting passage of solid particles therethrough when the column is in unpacked condition and preventing passage of gases therethrough in substantial volume at other times. This column operates on the principles disclosed in applications Serial Nos. 236,537-9 referred to above. Conduit 80 is connected at its upper end to the exhaust side of rotating element 6, i. e. to conduit 10. Conduit 80 is provided with a conduit 32 near its upper end provided with a valve 84. Conduit 80 is also provided with an upper vent 86 connected to conduit 80 by pipe 88 and provided with exhaust pipe 90 controlled by valve 92. Conduit 80 is also provided with a lower vent 94 connected to conduit 80 by pipe 96 and having an exhaust conduit 98 controlled by valve 100. Vents 86 and 94 are provided with metal screens or the like to permit the passage of gas therethrough but which will prevent passage of solid particles therethrough.

The lower end of vertical conduit 80 protrudes into a gas-tight reservoir 102. A conduit 104 is provided in the base of reservoir 102, said conduit being provided with a control valve 106. One end of conduit 104 is positioned so that gas passing from the end thereof will blow away or remove solid particles accumulated near the lower end of conduit 80. Conduit 56, which passes to the high pressure reactor 58 illustrated in Figure 4, connects to the inside of gas-tight receptacle 102 in the manner illustrated.

The operation of the apparatus illustrated in Figure 5 is identical to that illustrated in Figure 4 except for the operation of the vertical column 80 as a valve. In operating column 80 in conjunction with the balance of the apparatus, it will be assumed that initially a densely packed column of solid particles exists in vertical conduit 80 and that a body of solid particles is at the base of column 80 in reservoir 102. Also it will be assumed that conduit 56 is connected to high pressure reactor 58 of Figure 4 and that a high pressure exists therein. In such case conduit 80 is acting as a closed valve preventing passage of substantial amounts of gas from high pres sure reactor 58 into rotating unit 6. Therefore, valves 84 and 92 will be closed and valve 100 will be open so as to permit passage of gases which leak from high pressure reactor 58 into reservoir 102 thence in small quantities through vent 94. Valve 106 will also be closed.

In order to introduce solid particles into high pressure reactor 58, rotation of unit 6 is started in the manner previously described and solid particles are introduced into opening 32 to form a densely packed column inthe rotating arms. Element 6 is rotated as previously described. Valve 84 is then opened to permit high pressure gas to flow into the upper part of vertical conduit 80. This high pressure gas will flow partly into conduit 10 and thence through rotating member 6 to vents 38 and partly downward into vertical conduit 80 and into the vent 94 through the body of solids in this portion of conduit 80. At the same time gas will also continue to flow from high pressure reactor 58 through conduit 56, reservoir 102 and up through 80 into vent 94. Passage of gas through vent 94 is then terminated by closing valve 100, thus permitting the higher than system pressure previously established in the upper part of column 80 by introduction of gas through valve 84 to displace the packed solid particles from conduit 80. These displaced solid particles flow into reservoir 102 through conduit 56 and then into high pressure reactor 58. An extra conduit 104 and valve 106 for introducing fluidizing gas into reservoir 102 may be provided to assist in maintaining the solid particles therein in a fluidized condition during this transport stage.

With the rotating element discharge 10 at slightly higher than system pressure in reactor 58 and the packed column in conduit 80 displaced, transport gas is then introduced through pipe 20 to dislodge solid particles from rotating element 6 and to transport themdownwardly through conduit 80, thence into reservoir 102, conduit 56 and high pressure reactor 58. As this step is taken, pressuring gas valve 04 is closed. It is desirable that the rate of introduction of gas through conduit 20 be increased at approximately the same rate that the reduction in flow of gas through valve 84 takes place.

When it is desired to terminate passage of solid particles' from rotating element 6 through column 80 and thence into high pressure reactor 58, the introduction of gas through valve 106 is cut oflf. Also gas flow through conduit 20 to remove solid particles from rotating elernent 6 is gradually decreased. Simultaneously introduction of gas through conduit 82 is initiated and increased. The reduction of flow through conduit 20 and increase of flow through conduit 82 is about equal so as to maintain a pressure balance in the upper part of column 80. This will stop the flow of solid particles from rotating element 6 into conduit 80. Leakage of gas from conduit 82 will take place backwardly through rotating elernent 6, the packed coltunn therein and thence through vents 33 as described previously. Also, part of the gas from valve 84 will flow downwardly through conduit 80 and for a short interval of time this portion of the conduit will be more or less devoid of solid particles because of the purging action of this gas. Vent 86 is now opened gradually by opening valve 92. This gradually creates a decreasing pressure point in the portion of vertical conduit 30 adjacent conduit 38. Flow of gas from conduit 82 downwardly through conduit 80 and thence out through vent 86 and valve 92 will increase, and the flow of gas from conduit 82 down through conduit 80 and thence into conduit 56 and high pressure reactor 58 will decrease to zero and then reverse itself. Atthe same time, the flow of gas from conduit 82 into conduit 80 will remain constant. When the flow of gas reverses, as mentioned in the preceding sentence, solid particles in reservoir 102 will flow into column 80. The volume of solids in reservoir 102 must be sufficient to supply the volume of column 80 and cover the bottom of the column. These reverse flowing solid particles will be in a fluidized state, i. e. suspended in the gas, and when they trifugal force.

reach the level of conduit 88 the gas will flow out through vent 86. The solid particles are prevented from flowing out by the screen in vent 86. Therefore, these solid particles become de-aerated and a packed column of solid particles will form from vent 86 down through the column to the bottom of reservoir 102. Lower vent 94 is now put into operation by opening valve 100 and vent 86 is taken out of operation by closing valve 92. Pressuring gas is also cut 013? by closing valve 84.

At this stage a densely packed column of solid particles exists from vent 86 down to the bottom of reservoir 102. Also, a sufficient amount of solid particles exists in reservoir 102 to cover the lower end of the column and thus support it. Also the upper part of column 80, i. e. that portion adjacent vent 86, is now at' atmospheric pressure. Nevertheless, the high pressure existing in reactor 58, conduit 56 and reservoir 102 is prevented from blowing the solid particles out of column by vent 94 and the action of the densely packed column in dispersing the pressure against the Walls of the column as described above and in the copending patent applications herein referred to. The distance between vents 86 and 94 should be sufficient to permit the dispersal of this pressure differential. In the case of a pressure differential of 1000 p. s. i. and atmospheric, this distance should be about 12 to 15 feet.

My invention may be utilized for introducing solids of various types and sizes into high pressure systems. Thus the size of the particles can vary to a considerable extent and generally will have a mesh size between about and 400. The screen or filter used in the vent should be of such fineness as to prevent substantial flow of solid particles but permit the flow of gas. Thus the screen should have a mesh size smaller than the particles. 1

It is necessary to ensure at each point on the radius of rotating member 6 that the centrifugal force is at least equal to that developed at the same points by the pressure of the gas flowing in a reverse direction from the high pressure zone toward the center of the rotating member 6 and eventually out of vents 36. In other words the differential gas pressure force at each point in the rotating arm should be balanced or exceeded by the diiferential centrifugal force. The diiferential centrifugal force is linear with radius as illustrated in curve A of Figure 6. However, the dilferential force due to the pressure drop in the gas flowing through rotating member 6 in a reverse direction does not exhibit the same linear characteristics. At the low pressure end of the rotating member 6 (i. e. near opening 32 of Figure 1) this gas pressure gradient is quite high but at the high pressure end (i. e. near ends 8 of Figure 1) it is quite low. Curve B of Figure 6 illustrates the manner in which this gas pressure varies from the ends 8 of casing 6 to the opening 32. For this reason it is desirable to place the vents 36 at some distance from the central opening 32 and preferably at about the mid-point between the axis and the outer limits of the packed column. This will assure that the centrifugal force at any given point equals or exceeds the gas pressure at that point. Rotating member 6 is preferably tapered toward its outer periphery as illustrated in Figure l. The overall results is that in the compact column itself the centrifugal' forces at all points exceed the pneumatic pressure gradient at those points. The vents should be postioned so as to confine the gas pressure gradient to a portion of arms 6 where it can be easily offset by cen- The use of tapered ends for rotating arms 6 modify the pressure drop gradient so that it can be more easily adjusted to conform to the centrifugal force at any given point. The force acting against the vents may be made as low as desired by extending the depth of the recess for the vents so that there is a dispersion of stress by the increased distance in the compact column of solids in the vent.

The gas which passes through conduit 22 in Figure 1 and which is used to remove solid particles from the compact column must be at a slightly higher pressure than exists in the high pressure zone. In general this pressure difference need not be greater than about 50 to 60 p. s. i. although larger or smaller pressure differences may be used. This gas should be in such volume as to fluidize and transport the desired amount of solid particles away from the ends of the rotating casing 6 and into the high pressure zone as described. In other words at the extreme outward ends of the compact column where gas is introduced through conduit 22 of Figure 1, the pneumatically introduced force exceeds the centrifugal force imposed upon the suspension of gas and solid at these same points.

I claim:

1. The process for introducing solid particles into a high pressure system which comprises forming the solid particles into a compact column by centrifugal force, exposing that end of the compact column which is subjected to the highest centrifugal force to the high pressure existing in the high pressure system, adding solid particles to that end of the compact column which is subjected to the lowest centrifugal force, venting gas which leaks through the compact column from the high pressure system at a vent positioned intermediate the ends of the compact column, removing solid particles from the end of the compact column which is subjected to the highest centrifugal force and conveying the removed solid particles into the high pressure system.

2. The process for introducing solid particles into a high pressure system which comprises forming the solid particles into a compact column by centrifugal force, exposing that end of the compact column which is subjected to the highest centrifugal force to the high pressure existing in the high pressure system, adding solid particles to that end of the compact column which is subjected to the lowest centrifugal force, venting gas which leaks through the compact column from the high pressure system at a vent positioned intermediate the ends of the compact column, removing solid particles from the end of the compact column which is subjected to the highest centrifugal force by exposing the end of the compact column which is subjected to the highest centrifugal force to a current of high pressure gas whereby solid particles are removed from the compact column and are suspended in the current of gas, and introducing the current of gas with suspended particles into the high pressure system.

3. The process for introducing solid particles into a high pressure system which comprises forming the solid particles into a compact column by centrifugal force, exposing that end of the compact column which is subjected to the highest centrifugal force to the high pressure existing in the high pressure system, adding solid particles to that end of the compact column which is subjected to the lowest centrifugal force, venting gas which leaks through the compact column from the high pressure system at a vent positioned intermediate the ends of the compact column and positioned so as to maintain pneumatic pressure at all points along the compact column at a value below the centrifugal pressure at the same points, removing solid particles from the end of the compact column which is subjected to the highest centrifugal force by directing a high pressure jet of gas into the compact column so as to suspend the particles in the gas, passing this suspension to a zone of lower centrifugal force while maintaining the pressure of the transport gas at any point at a higher value than the centrifugal force at the same point, and conveying the suspension of solid particles into the high pressure system.

4. In a means for conveying solid particles from a low pressure zone to a high pressure zone Without substantial flow of gas therethrough which includes a continuous compact column of solid particles and a vent for gas positioned intermediate the ends of the column and means associated with the vent for preventing How of solid particles through the vent, that improvement which comprises an axially mounted rotatable chamber adapted to hold a compact column of solid particles, means for introducing solid particles into the rotating chamber at a point near the axis of the rotating chamber and into one end of the compact column, means for removing solid particles from the opposite end of the compact column at a point in the rotatable chamber removed from the axis and means for conveying the removed solid particles into the high pressure zone' 5. In a means for conveying solid particles from a low pressure zone to a high pressure zone without substantial flow of gas therethrough which includes a continuous compact column of solid particles and a vent for gas positioned intermediate the ends of the column and means associated with the vent for preventing flow of solid particles through the vent, that improvement which comprises an axially mounted cylindrical rotatable chamber which tapers toward each end thereof and which is adapted to hold a compact column of solid particles, means for introducing solid particles into the rotating chamber at a point near the axis of the rotating chamber and into one end of the compact column, means for introducing a gas stream into the column of solid particles at a point in the rotatable chamber removed from the axis and means for conveying the stream of gas and removed solid particles into the high pressure zone.

6. Means for conveying solid particles from a low pressure zone to a high pressure zone without substantial flow of gas thcrethrough which comprises a combination an axially mounted cylindrical rotatable chamber which is adapted to hold a compact column of solid particles, a vent for gas positioned intermediate the ends of the rotatable chamber, means associated With the vent for preventing flow of solid particles through the vent, means for introducing solid particles into the rotatable chamber at a point near the axis of the rotatable chamber, means for introducing a stream of gas into the rotatable chamber at a point in the rotatable chamber removed from the axis, a vertical conduit, means for conveying a stream of gas and suspended solid particles from said point in the rotatable chamber removed from the axis and into the top of said vertical conduit, two vents for gas positioned intermediate the ends of said vertical conduit and spaced from each other, screens for preventing flow of solid particles through said vents, valves to control flow of gas through the vents, means for introducing gas under pressure into the top of the vertical conduit, a reservoir for solids connected to the lower end of the vertical conduit and means for conveying solids from said reservoir to the high pressure zone.

I References Cited in the file of this patent UNITED STATES PATENTS 2,536,402 Voorhies Ian. 2, 1951 2,684,873 Berg July 27, 1954 2,716,050 Hagerbanmer Aug. 23, 1955 

1. THE PROCESS FOR INTRODUCING SOLID PARTICLES INTO A HIGH PRESSURE SYSTEM WHICH COMPRISES FORMING THE SOLID PARTICLES INTO A COMPACT COLUMN BY CENTRIFUGAL FORCE, EXPOSING THAT END OF THE COMPACT COLUMN WHICH IS SUBJECTED TO THE HIGHEST CENTRIFUGAL FORCE TO THE HIGH PRESSURE EXISTING IN THE HIGH PRESSURE SYTEM, ADDING SOLID PARTICLES TO THAT END OF THE COMPACT COLUMN WHICH IS SUBJECTED TO THE LOWEST CENTRIFUGAL FORCE, VENTING GAS WHICH LEAKS THROUGH THE COMPACT COLUMN FROM THE HIGH PRESSURE SYTEM AT A VENT POSITIONED INTERMEDIATE THE ENDS OF THE COMPACT COLUMN, REMOVING SOLID PARTICLES FROM THE END OF THE COMPACT COLUMN WHICH IS SUBJECTED TO THE HIGHEST CENTRIFUGAL GORCE AND CONEYING THE REMOVED SOLID PARTICLES INTO THE HIGH PRESSURE SYTEM. 